This disclosure relates to a fuel vapor treating apparatus generally mounted on a vehicle such as an automobile.
A conventional fuel vapor treating apparatus has an adsorbent canister capable of adsorbing and desorbing fuel vapor from a fuel tank, a fuel vapor path, connecting the adsorbent canister to the fuel tank, and a diaphragm valve configured to close and open the fuel vapor path (for example, Japanese Laid-Open Patent Publication No. 11-208293).
In a conventional fuel vapor treating apparatus, inner pressure of the fuel tank acts on a pressure control chamber in order to open the diaphragm valve during refueling. Then, gas having a content of fuel vapor flows from the fuel tank into the adsorbent canister. In such a configuration, it is difficult to achieve improvements in both (1) ease of refueling and (2) sealing capability when the diaphragm is closed. That is, the ease of refueling can be improved by decreasing opening pressure in the diaphragm valve. However, this configuration lowers the sealing ability of the closed diaphragm valve. Therefore, inner gas in the fuel tank leaks into the adsorbent canister after refueling using a gas pump. This results in a rather low liquid fuel, level in the inlet pipe of the fuel tank. In this situation, an operator can additionally add fuel by further operation of the gas fuel pump, however, there is a possibility that excessive refueling may occur. In contrast, sealing ability can be improved by increasing the opening pressure of the diaphragm valve. This, however, increases the pressure level during refueling and can thereby result in increased refueling difficulty. Accordingly, there has been a need for an improved fuel vapor treating apparatus.